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Reducing Weather Helm

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Bruce Baker
Captain

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USA
402 Posts

Initially Posted - 07/07/2005 : 15:36:38

The last two races on the Potomac have had unusually high 15 knot winds--usually it's under 5. On both races, I've been a bit overpowered with my 150 genoa. I noted that when I pushed down on the tiller we got speeds of 7 knots. When I pulled hard on the tiller, the knot meter dropped to 1.5 knots. Obviously, I'd like to try to get better balance so that I'm not slamming on the brakes every ten seconds. I've had the traveller down and the outhaul tight. Any other ideas?

Thanks,

Bruce Baker
Falls Church, VA
"Yee Ha" 3573
'83SR/SK

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 07/07/2005 : 16:26:31

There are a number of things you can do to reduce weatherhelm. [url="http://www.catalina25-250.org/tech/snkhelm.html"]Check out this article on Weatherhelm by Bill Holcomb.[/url] It has a lot of good info.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 07/09/2005 : 11:27:53

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Bruce Baker
 ...I noted that when I pushed down on the tiller we got speeds of 7 knots. When I pulled hard on the tiller, the knot meter dropped to 1.5 knots.<hr height="1" noshade id="quote"></blockquote id="quote">
Hmmm... Did you mean the meter dropped by 1.5 knots? 7 to 1.5 would be quite a swing! An expert racer (and rigger) once told me a little weather helm (around 5 degrees on the tiller) adds to performance by increasing the lift from the keel. Any good racer will also tell you to minimize your helm corrections, allowing puffs to push you to weather (via the boat's weather helm) and lulls to let you fall off, and figuring out the average track that'll take you to the mark or the lay line. You can see that happening in the tracks of the America's Cup boats on the web-casts of the races--they wiggle all over the place as the helmsman minimizes drag.

Edited by - Dave Bristle on 07/09/2005 11:30:54

Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 07/09/2005 : 13:01:18

Excessive weather helm is usually either caused by a rig that is out of tune or by a sailplan that is out of balance, or by sails that aren't well-trimmed. If it's a rig-tuning problem, then re-adjust the rig so that it tilts slightly more forward to reduce the tiller pressure. If the sailplan is out of balance, you might need to reduce the sail area, first by reefing the mainsail, and, if the helm is still heavy, by reducing the size of the jib. If it's a sail trim problem, then Dave's article is an excellent resource.

You'll notice that all of these suggestions are generally aimed at doing two things: 1) reducing the amount of heel, and 2) reducing the size and power of the mainsail in relation to the size and power of the jib. Generally, the mainsail is more responsible for excessive weather helm than the jib, and that's why you want to reduce its effect by rig tuning, balancing the sailplan and sail trim.

Edited by - on

Bill Holcomb
Admiral

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USA
769 Posts

Response Posted - 07/10/2005 : 09:56:31

Hi Bruce,

In addition to Steve's suggestions, take a close look at your sails. If they are old, they may have a very round shape with the max depth of the draft at or aft of midway on the sail. This may be ok for day-sailing, but not for racing effectively. The round shape cannot be adjusted flat like new sails can. So, a lot of the energy developed by the old sails is sideways not forward. Your boat heels more; the boat will be slower than others AND not point as high.

Bill Holcomb - C25 Snickerdoodle #4839

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 07/10/2005 : 12:30:32

This is a really interesting subject.

Folks often report that when the boat heels, the rudders effects are both lateral (port or stbd) and vertical (as the rudder heels with the boat, some of it's force is directed to either pushing the transom up or pushing it down). Certainly this is the case.

But I'm always curious about the notes on the hull developing a movement to windward when heeling.

Here's an alternative concept...

The fore & aft curve of the hull is generally much flatter along the keel, and the curve increases nearer to the regular waterline. So when the hull is heeling then the curve of the hull on the leeward side in the water is close to maximum and the curve to windward is much less.

This seems to mimic a wing. The line along the curve on the leeward side is longer than the windward side, so the water has to flow faster around the port side and thus a 'lift' to port is developed.

This would indicate that the boat would have a tendency to move to leward as it heels.

(excluding any other forces)

May the force be with you.

Edited by - on

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.